Cycloisomerization of Aromatic Homo- and Bis-homopropargylic Alcohols via Catalytic Ru Vinylidenes: Formation of Benzofurans and Isochromenes
作者:Alejandro Varela-Fernández、Carlos González-Rodríguez、Jesús A. Varela、Luis Castedo、Carlos Saá
DOI:10.1021/ol902212h
日期:2009.11.19
Ru-catalyzed cycloisomerizations of aromatic homo- and bis-homopropargylic alcohols effectively afford benzofurans and isochromenes. These processes proved to be chemo- and regioselective (5-, and 6-endo cyclizations) derived from key Ru vinylidene intermediates. The presence of an amine/ammonium base−acid pair is crucial for the catalytic cycle.
Bimolecular coupling reactions through oxidatively generated aromatic cations: scope and stereocontrol
作者:Yubo Cui、Louis A. Villafane、Dane J. Clausen、Paul E. Floreancig
DOI:10.1016/j.tet.2013.05.011
日期:2013.9
Chromenes, isochromenes, and benzoxathioles react with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone to form stable aromatic cations that react with a range of nucleophiles. These oxidative fragment coupling reactions provide rapid access to structurally diverse heterocycles. Conducting the reactions in the presence of a chiral Bronsted acid results in the formation of an asymmetric ion pair that can provide enantiomerically enriched products in a rare example of a stereoselective process resulting from the generation of a chiral electrophile through oxidative carbon hydrogen bond cleavage. (C) 2013 Elsevier Ltd. All rights reserved.